1. Field of the Invention
The present invention is directed to an oil mist eliminator for removing oil mist from a contaminated air and discharge a clean air removed of the oil mist, and more particularly to such an oil eliminator using an impeller which diverts an air flow for separating the oil mist from the contaminated air.
2. Description of the Prior Art
U.S. Pat. No. 5,207,809 discloses an oil mist eliminator using an impeller or fan for separating the oil mist from an oil-contaminated air while changing flow directions. The oil eliminator includes a casing with an inlet and an outlet, and an impeller which is accommodated within the casing and is driven to rotate about a rotation axis of the impeller for drawing the contaminated air from the inlet and discharge a clean air removed of the oil mist out through the outlet. The impeller is of a front-in and rear-out type which draws the air from a front opening of the impeller and vents the clear air rearwards with respect to the rotation axis. In detail, as shown in FIGS. 7 and 8 of the attached drawings, the impeller is composed of a front disc 40P with a center opening 42P, a rear disc 50P coaxial with the front disc, and a plurality of blades 60X which are circumferentially spaced and secured between the front and rear discs. The rear disc 50P is provided with a hub 52P receiving a motor output shaft for rotating the impeller in one direction. Each blade 60P is shaped into a generally L-shaped with an inner fin 68P extending radially between the front and rear discs and an outer fin 61P which is bent from an inner fin 68P towards the rotating direction. The outer fin 61P projects radially outwardly of the discs to deflect a radial air flow guided between adjacent inner fins 68P so as to deposit the oil mist on the outer fin 61P by collision of the oil-laden air against the outer fin, while permitting the air flow in the deflected direction. The outer fin 61P is twisted so as to deflect the air axially rearward for discharging the air out through the outlet. With this arrangement, however, there remains a problem that the air (indicated by arrows in FIG. 8) drawn through the center opening and guided radially outwardly adjacent along the rear disc 50P may partially escape rearwards past the outer circumference of the rear disc without colliding against the outer fin, i.e., without a chance of separating the oil mist from the air. Thus, the oil mist may be still carried on the air being discharged out through the outlet, thereby lowering separation efficiency.
In view of the above insufficiency, the present invention has been accomplished to provide an oil mist eliminator which is capable of separating the oil mist successfully and efficiently. The oil mist eliminator in accordance with the present invention includes a casing with an inlet and an outlet, and an impeller which is accommodated within the casing and is driven to rotate about a rotation axis for drawing an oil-contaminated air through the inlet and discharging a clean air removed of the oil mist out through the outlet. The impeller is composed of a rear disc provided at its center with a hub for receiving a rotating shaft in registration with the rotation axis, a front disc spaced forwardly of the rear disc in a coaxial relation thereto. The front disc has a center front opening in registration with the inlet for drawing the contaminated air. The impeller includes a plurality of circumferentially spaced blades which are secured between the rear disc and the front disc. Each of the blades is of a generally L-shaped configuration having an inner fin extending generally in a radial direction of the impeller and an outer fin which is bent from the inner fin in a rotating direction of the impeller. The outer fin projects radially outwardly of the rear and front discs to deflect a radial air flow proceeding between the adjacent inner fins so as to deposit the oil mist or the oil particles upon the outer fin by collision against the outer fin, while permitting the clean air removed of the oil mist to flow in a deflected direction.
The characterizing feature of the present invention resides in that the outer fin is twisted with respect to a tangential direction on the circumference of the impeller in a forward direction along the rotation axis such that the outer fin has its inside surface facing in the forward direction, thereby directing the clean air axially forwardly to discharge the same out through the outlet. Thus, the impeller is configured to be of a front-in and front-out type which draws the contaminated air from the front opening and deflect the clean air back in the axially forward direction. With this structure, the contaminated air proceeding axially through the center opening and then being guided radially along the rear disc can be successfully directed towards the outer fin and merge into the axially forward air flow being discharged out from the impeller, thereby minimizing a chance of the air flow partially escaping through the circumference of the impeller without colliding against the outer fin and therefore improving separation efficiency of depositing the oils mist on the outer fin.
Preferably, a bent line along which the outer fin is bent from the inner fin is inclined with respect to the rotation axis such that bent line has a radial distance from said rotation axis which is greater towards its front end than at its rear end. This is advantageous in that the outer fin can have the inside air deflecting surface of increased area within a limited axial dimension between the rear and front discs. In this connection, the outer fin may be shaped to have its front end projecting forwardly beyond a plane of the front disc to give an increased surface area to the inside surface responsible for diverting the air flow.
Further, the width of the outer fin defined between the bent line and an outer circumferential edge of the outer fin may be made greater towards the front end of the outer fin than at the rear end thereof, for efficiently producing the air flow back in the axially forward direction with an attendant enhancement of oil separation efficiency.
The front disc may be additionally shaped to have its outer periphery bent rearwards to form thereat a baffler rim which is inclined with respect to the front disc in order to impede the air flow proceeding radially along the front disc from escaping out through the impeller without colliding against the outer fin.
These and still other objects and advantageous features of the present invention will become more apparent from the following description of the preferred embodiment when taken in conjunction with the attached drawings.